1. Field of the Invention
This invention relates to a process for forming an image, and especially, to a method for obtaining a relief image which comprises imagewise exposing a photosensitive image-forming material and subjecting it to dry development.
2. Brief Discussion of the Prior Art
The present invention relates to a process for forming an image, which comprises imagewise exposing a photosensitive image-forming material composed of a support having formed thereon a layer of a photosensitive composition containing a diazonium compound or an aromatic azide compound and a thermoplastic binder and adhering the photosensitive composition layer closely to a development carrier sheet having a layer of an adhesive composition; or imagewise exposing said photosensitive image-forming material with said carrier sheet in intimate contact; and then peeling said image-forming material and said carrier sheet from each other to transfer and adhere the exposed area of the photosensitive composition layer to the carrier sheet and thereby form a relief image on it, and simultaneously form a relief image corresponding to the non-transferred, non-exposed area of the photosensitive composition on the support.
Many methods for forming images by the dry-method development of a photosensitive compositions have been suggested heretofore which include, for example, developing an exposed photosensitive material by heating a "thermodeveloping method", with a suitable radiation ray, with a gas, with an electrostatic treatment, and by the application of pressure.
One typical dry developing method is a so-called peeling development process wherein a photosensitive image-forming material composed of a support, a layer of a photosensitive composition on the support and a cover sheet placed on the photosensitive layer in which the adhesion of the photosensitive layer to the support and to the cover sheet changes by exposure, and after exposure, peeling the support and the cover sheet from the photosensitive layer to leave only the exposed area on the support or the cover sheet and the unexposed area on the other, both as a relief image.
The method of image formation by peeling development is operated in the dry state, and the operation is simpler than ordinary liquid development using a large quantity of water or solvent. Furthermore, only the image area of the photosensitive image-forming composition which remains on the support after peeling, the non-image area is removed from the support by the peeling operation. Accordingly, this method has the advantage that the stabilization of the non-image area essential to photosensitive materials developed by an ordinary liquid developing method or thermodeveloping method, that is, its fixation, can be performed simultaneously with the developing operation. Since in the peel developing method, the photosensitive composition in the non-image area is fixed to the peel sheet as a solid layer, it can be disposed of easily, and this is desirable from the standpoint of environmental preservation. When the composition contains useful ingredients, they can be completely recovered and easily reused. Thus, this processing method is advantageous from the viewpoint of saving resources, too.
Since a general procedure for image formation by peeling was published in Japanese Patent Publication No. 9663/63, a number of specific techniques have been suggested. These techniques are classified by their basic characteristics, and briefly described below.
A three-layer structure composed of a support, a photosensitive layer on it containing a photopolymerizable monomer and a cover sheet laminated to the photosensitive layer constitutes a very important field in the art. Peel development of this photosensitive material is performed by utilizing the fact that polymerization proceeds in the exposed area of the material, and, therefore, the adhesion of the photosensitive layer to the support and to the cover sheet differs between the exposed area and unexposed area. It is described, for example, in Japanese Patent Publication No. 3193/62 (U.S. Pat. No. 3,060,024), Japanese Patent Publication No. 22901/68 (U.S. Pat. No. 3,353,955), Japanese Patent Application (OPI) No. 7728/72 (The term "OPI" as used herein refers to a "published unexamined Japanese patent application") (U.S. Pat. No. 3,770,438), and U.S. Pat. Nos. 3,060,023 and 3,525,615. U.S. Pat. Nos. 3,627,529, 3,591,377 and 3,607,264, etc., disclose a similar peel-developable photosensitive material consisting essentially of a support, a photosensitive layer and a transparent cover sheet in which the photosensitive composition layer contains a photocurable polyester (U.S. Pat. No. 3,591,377), a photocurable olefin compound (U.S. Pat. No. 3,607,264) or a photocuring catalyst and a thiol-containing olefin polymer (U.S. Pat. No. 3,627,529).
The methods described above perform peel development by utilizing changes in adhesion incident to the photochemical reaction of a photopolymerizable monomer or a photocurable compound.
Methods using other photosensitive compounds are also known. For example, Japanese Patent Application (OPI) No. 57819/77 discloses a method which comprises using a laminate structure composed of a sheet consisting of a support and an adhesive composition layer formed thereon, and a transparent plastic film coated with a photosensitive composition comprising a diazonium salt and a binder, exposing the laminate structure, and then peeling the film thereby to leave the unexposed area of the photosensitive composition layer on the transparent plastic film and the exposed area on the support.
Japanese Patent Application (OPI) No. 3215/78 discloses an invention relating to a method which uses a similar sheet composed of a support and an adhesive composition layer formed thereon. A thin film layer comprising a metal or chalcogen is further provided between the support and a photosensitive composition layer to form a five-layer laminate structure. It utilizes the phenomenon that peel development after exposure induces selective separation at the interface between the non-sensitive thin film layer and the support.
In the invention disclosed in Japanese Patent Application (OPI) No. 23632/78, a photosensitive composition containing a polyhalogen compound and a polymer having a phenol nucleus is used, and by peeling a transparent film-like material adhering to the photosensitive composition layer before or after exposure, an image corresponding to the exposed image is obtained on the support.
British Pat. No. 1,319,295 discloses a peel developing method which comprises laminating a heat-softenable polymeric layer and a powder capable of absorbing infrared rays to a support, exposing the resultant material to infrared rays to impart tackiness imagewise to the heat-softenable polymeric layer, and separating the polymeric layer from the support to form an image on the support.
So far, the characteristics of known techniques about image formation by peeling have been described. Hetertofore, the basic principle of peel development has been considered to lie in the changing of the adhesion between the photosensitive composition layer and the support by light. For example, according to peel development, a photopolymerizable or photocurable photosensitive composition is used, and by a photochemical composition at the exposed area, the adhesion of the photosensitive layer to the support is decreased or increased from that before exposure, whereby the exposed area and the unexposed area are formed as images separated on different supports. Accordingly, a method for forming an image was suggested which comprises exposing a photosensitive composition in intimate contact with a cover sheet and peeling the cover sheet by utilizing the fact that the photosensitive adhesive layer has suitable tackiness at room temperature.
On the other hand, Japanese Patent Application (OPI) Nos. 57819/77 and 141003/76 and 3215/78 (U.S. patent application Ser. No. 810,828, filed June 28, 1977), for example, disclose a method in which the adhesive quality of the photosensitive composition layer itself is not essential. The adhesion required for peeling development is obtained by providing a cover sheet with a pressure-sensitive adhesive layer. The adhesive cover sheet is adhered intimately to the photosensitive composition layer before or after imagewise exposure, and then peeled off. Accordingly, a broader range of selection for the characteristics of the photosensitive composition is possible than the aforesaid methods which use a photopolymerizable compound as a material and utilize the tackiness of the photosensitive composition layer itself at ordinary temperatures.
Some techniques which perform the separation of an image more effectively by heating the image-forming material at the time of peeling have been disclosed. For example, U.S. Pat. No. 3,060,023 discloses a method which comprises using a mixture of a photopolymerizable monomer and a thermoplastic polymer as a photosensitive composition layer, and afterexposure, bringing the photosensitive layer into intimate contact with a receptor sheet at a temperature of at least 40.degree. C. thereby to soften the unexposed area, i.e., the unpolymerized area of the photopolymerizable monomer, selectively and to transfer the image thermally onto the receptor sheet. It is clearly seen from the disclosure of the specification that this technique utilizes the transfer of the unexposed area (unpolymerized area) of the thermoplastic photopolymerizable composition to the receptor sheet under heat, and it affords a number of copies by bringing the exposed photopolymerizable composition layer into contact with a suitable support to transfer the unexposed area under heat. Since in this method a transfer image composed of the unpolymerized area is always utilized as an image, when it is desired to utilize the image obtained on the support further for a printing plate or a photoresist, it is necessary to provide an additional step of curing the transferred image by an after-treatment such as exposure.
Japanese Patent Application (OPI) No. 39025/76 discloses a method which comprises imagewise exposing a three-layer image-forming material composed of a metal substrate, a layer of a photosensitive composition comprising an addition-polymerizable monomer and polyvinyl butyral and a cover sheet, and peeling the exposed material while heating it, thereby to induce cohesive destruction of the unexposed area (i.e., unpolymerized area) of the photosensitive layer and to obtain the same positive image as used in imagewise exposure on the metal substrate which image is utilized as a photoresist image.
Thus, there have been examples in which heating is performed at the time of peeling. All of these examples use a layer of a photopolymerizable composition, and facilitate the transfer of an image to an image-receiving sheet by increasing the flowability of the unexposed area through heat.
The present invention relates to a process for forming an image, which comprises imagewise exposing a photosensitive image-forming material composed of a support and formed thereon a layer of a photosensitive composition containing a diazonium compound or an aromatic azide compound and a thermoplastic binder and then adhering the photosensitive composition layer closely to a carrier sheet having a layer of an adhesive composition; or imagewise exposing said photosensitive image-forming material in intimate contact with said carrier sheet; and then peeling said image-forming material and said carrier sheet from each other to transfer and adhere the exposed area of the photosensitive composition layer to the development carrier sheet and to form a relief image on it, and simultaneously form a relief image corresponding to the non-transferred, non-exposed area of the photosensitive composition on the support.
Japanese Patent Application (OPI) No. 57819/77 discloses a method for image formation by peeling operation in which a diazonium compound is used as a photosensitive substance. This method relies upon a photosensitive image-forming material composed of a support, an adhesive composition thereon, a photosensitive layer and a transparent plastic film, and comprises peeling the plastic film from the laminate after imagewise exposure whereby the unexposed area of the photosensitive composition layer adheres to the adhesive layer, and the exposed area of the photosensitive composition layer remains on the support. While the photosensitive composition used in conventional image-forming methods by a peeling operation are limited to photopolymerizable or photohardenable compositions, the Japanese (OPI) relies on a film having an dhesive composition layer as a means for obtaining relief images upon peeling development of a photosensitive composition layer composed of a combination of 4-(p-tolylthio)-2,5-dibutoxybenzenediazonium chloride/zinc chloride double salt or an aromatic azide compound and a binder polymer. In this invention, the exposed areas of the photosensitive composition remain on the support and the corresponding unexposed areas adhere adhesive composition layer on the carrier sheet, as a separate relief image.